SQL> SELECT * FROM V$VERSION;

BANNER
----------------------------------------------------------------
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
PL/SQL Release 9.2.0.4.0 - Production
CORE	9.2.0.3.0	Production
TNS for IBM/AIX RISC System/6000: Version 9.2.0.4.0 - Production
NLSRTL Version 9.2.0.4.0 - Production

CREATE TABLE LISTE_ELM 
(
  COD_LISTE VARCHAR2(2 BYTE) NOT NULL 
, COD_ELM VARCHAR2(2 BYTE) NOT NULL 
, CONSTRAINT LRE_PK PRIMARY KEY 
  (
    COD_LISTE 
  , COD_ELM 
  )
  ENABLE 
) 

CREATE UNIQUE INDEX LRE_PK ON LISTE_ELM (COD_LISTE ASC, COD_ELM ASC) 

REM INSERTING into LISTE_ELM
SET DEFINE OFF;
Insert into LISTE_ELM (COD_LISTE,COD_ELM) values  ('LA','EA');
Insert into LISTE_ELM (COD_LISTE,COD_ELM) values  ('LB','EB');
Insert into LISTE_ELM (COD_LISTE,COD_ELM) values  ('LC','EC');
Insert into LISTE_ELM (COD_LISTE,COD_ELM) values  ('LC','ED');
Insert into LISTE_ELM (COD_LISTE,COD_ELM) values  ('LC','EE');
Insert into LISTE_ELM (COD_LISTE,COD_ELM) values  ('LD','EF');
Insert into LISTE_ELM (COD_LISTE,COD_ELM) values  ('LD','EG');
Insert into LISTE_ELM (COD_LISTE,COD_ELM) values  ('LD','EH');
Insert into LISTE_ELM (COD_LISTE,COD_ELM) values  ('LE','EG');
Insert into LISTE_ELM (COD_LISTE,COD_ELM) values  ('LF','EH');
Insert into LISTE_ELM (COD_LISTE,COD_ELM) values  ('LH','EH');

CREATE TABLE ELM_LISTE 
(
  COD_ELM VARCHAR2(2 BYTE) NOT NULL 
, COD_LISTE VARCHAR2(2 BYTE) NOT NULL 
, CONSTRAINT ERL_PK PRIMARY KEY 
  (
    COD_ELM 
  , COD_LISTE 
  )
  ENABLE 
) 

CREATE UNIQUE INDEX ERL_PK ON ELM_LISTE (COD_ELM ASC, COD_LISTE ASC) 

REM INSERTING into ELM_LISTE
SET DEFINE OFF;
Insert into ELM_LISTE (COD_ELM,COD_LISTE) values ('EA','LB');
Insert into ELM_LISTE (COD_ELM,COD_LISTE) values ('EB','LC');
Insert into ELM_LISTE (COD_ELM,COD_LISTE) values ('EG','LF');
Insert into ELM_LISTE (COD_ELM,COD_LISTE) values ('EH','LH');

the lines (LA,EA), (LB,EB), (LC,EC), (LC,ED), (LC,EE) from LIST_ELM, and the lines (EA,LB), (EB,LC) from ELM_LIST.

Table LIST_ELM :
(LA,EA)
(LB,EB)
(LC,EC)
(LC,ED)
(LC,EE) 

Table ELM_LIST : 
(EA,LB), 
(EB,LC)

with
  list_elm(a, b) as (
    select 'LA' , 'EA' from dual
    union all select 'LB' , 'EB' from dual
    union all select 'LC' , 'EC' from dual
    union all select 'LC' , 'ED' from dual
    union all select 'LC' , 'EE' from dual
    ),
  elm_list(a, b) as (
    select 'EA' , 'LB' from dual
    union all select 'EB' , 'LC' from dual
    ),
  combine(t, a, b) as (
    select 'list_elm', a.* from list_elm a
    union all select 'elm_list', a.* from elm_list a)
select
  t,
  lpad(' ', level * 2, ' ') || a || ' - ' || b as r
  from combine a
  connect by prior b = a and t <> prior t
  start with t = 'list_elm' and a = 'LA'

----------+-------------------
T         |R                  
----------+-------------------
list_elm  |  LA - EA          
elm_list  |    EA - LB        
list_elm  |      LB - EB      
elm_list  |        EB - LC    
list_elm  |          LC - EC  
list_elm  |          LC - ED  
list_elm  |          LC - EE  

SQL> with
  2    list_elm(a, b) as (
  3      select 'LA' , 'EA' from dual
  4      union all select 'LB' , 'EB' from dual
  5      union all select 'LC' , 'EC' from dual
  6      union all select 'LC' , 'ED' from dual
  7      union all select 'LC' , 'EE' from dual
  8      ),
  9    elm_list(a, b) as (
 10      select 'EA' , 'LB' from dual
 11      union all select 'EB' , 'LC' from dual
 12      ),
 13    combine(t, a, b) as (
 14      select 'list_elm', a.* from list_elm a
 15      union all select 'elm_list', a.* from elm_list a)
 16  select
 17    t,
 18    lpad(' ', level * 2, ' ') || a || ' - ' || b as r
 19    from combine a
 20    connect by prior b = a and t <> prior t
 21    start with t = 'list_elm' and a = 'LA'
 22  /
  list_elm(a, b) as (
          *
ERROR at line 2:
ORA-32033: unsupported column aliasing

SQL> col col1 format a4
SQL> col col2 format a4
SQL> with
  2    data as (
  3      select 'LISTE_ELM' tab, cod_liste col1, cod_elm col2
  4      from liste_elm
  5      union all
  6      select 'ELM_LISTE', cod_elm, cod_liste
  7      from elm_liste
  8    )
  9  select tab, col1, col2
 10  from data
 11  connect by prior tab != tab and prior col2 = col1
 12  start with tab = 'LISTE_ELM' and col1 = 'LA'
 13  order by row_number() over (order by tab desc)
 14  /
TAB       COL1 COL2
--------- ---- ----
LISTE_ELM LA   EA
LISTE_ELM LB   EB
LISTE_ELM LC   EC
LISTE_ELM LC   ED
LISTE_ELM LC   EE
ELM_LISTE EA   LB
ELM_LISTE EB   LC

7 rows selected.

SQL> with
  2    data as (
  3      select 'LISTE_ELM' tab, cod_liste col1, cod_elm col2
  4      from liste_elm
  5      union all
  6      select 'ELM_LISTE', cod_elm, cod_liste
  7      from elm_liste
  8    ),
  9    result1 as (
 10      select tab, col1, col2,
 11             row_number() over (partition by tab order by null) rn
 12      from data
 13      connect by prior tab != tab and prior col2 = col1
 14      start with tab = 'LISTE_ELM' and col1 = 'LA'
 15    ),
 16    merge1 as (
 17      select tab, sys_connect_by_path('('||col1||','||col2||')','#') res, level lvl
 18      from result1
 19      connect by prior tab = tab and prior rn = rn-1
 20      start with rn = 1
 21    ),
 22    merge2 as (
 23      select tab, substr(res,2) res, lvl, max(lvl) over (partition by tab) max_lvl
 24      from merge1
 25    ),
 26    result2 as (
 27      select tab, res res
 28      from merge2
 29      where lvl = max_lvl and rownum > 0
 30    )
 31  select (select res from result2 where tab = 'LISTE_ELM')||'/'||
 32         (select res from result2 where tab = 'ELM_LISTE') res
 33  from dual
 34  /
RES
---------------------------------------------------------------------------------------
(LA,EA)#(LC,ED)#(LC,EE)#(LC,EC)#(LB,EB)/(EA,LB)#(EB,LC)

1 row selected.